Machinery for packaging food, pharmaceuticals, or other products which must be handled in a hygienic manner is well known. Typically, such machinery has certain parts, such as gears, motors, bearings, etc., which must be present to provide a working machine and yet should not be exposed to the product being hygienically packaged. Typically, these are moving machine elements which are difficult to clean. Commonly, it is also desirable to prevent contamination of the non-hygienic areas with the hygienic product. A barrier must be maintained between the hygienic and non-hygienic areas of the machine to address these goals.
The job of designing a suitable barrier is more complicated when the machine has moving parts which regularly move back and forth between the hygienic and non-hygienic areas (as is commonly the case). In that situation, the barrier between the hygienic and non-hygienic areas of the machine has included seals, collapsible bellows, or other elements to maintain isolation between the hygienic and non-hygienic areas along portions of the machinery passing through the barrier.
An even more difficult situation arises when ultrasonic energy is transmitted from a generator in the non-hygienic area of the machine into the hygienic area through a barrier between the respective areas. Simply providing a seal which wipes an ultrasonic transducer projecting through a barrier wall will not suffice: the ultrasonic energy carried by the transducer can damage the seal rapidly and breach the barrier. Other expedients, such as a bellows seal between moving pans, also may be damaged when one of the parts carries ultrasonic energy. A bellows seal exposed to the hygienic area is also difficult to keep clean or to inspect for integrity, and thus may be unsatisfactory for use in the hygienic area of a machine.